They occur in nearly any complex environment and may be acting as source rock, reservoir or cap rock.

UNESCO: EARTH SCIENCES FOR SOCIETY

We believe that blue-sky potential lurks in companies operating in the Middle East with expertise in unconventional production, access to good source rock, and management that can marry the two.

FORBES: Unconventional Oil In The Middle East

Fracking involves the injection of water containing a surfactant and various other chemicals under high pressure into a source rock e.g. shale, causing the latter to fracture and release natural gas (principally methane).

FORBES: British "Fracking" Causes Earthquake -- What Now?

At the same time Yury Boiko, the Ukrainian energy minister, has high hopes that shale gas -- formed deep underground within large shale rock formations -- could also be a major alternative source of power in the decades to come.

CNN: STORY HIGHLIGHTS

Her husband, Denis Thatcher, whom she married in 1951 and by whom she had a son and daughter, was not exactly dashing but he was rich (oil industry), a capable businessman, a rock on which she could always lean in bad times, and a source of funny 19th-hole sayings.

WSJ: Paul Johnson: The World-Changing Margaret Thatcher

Hit the source link to grab a Radio-enabled preview build and see if some algorithm can defeat even the mightiest Yacht Rock playlist crafted by our own Brian Heater.

ENGADGET: Spotify Radio feature turns into an app, offers Pandora-like stations with unlimited skips